Don't know sepcifically about your car, but most Mercedes that have a high speed based on coolant temp typically come on at around 230. Low speed is usually based on refrigerant temp in the A/C for dual speed fans. The mechanical fan clutch is set to engage at a lower temp.

If you are not getting much above 200, then it's not broken, it's functioning as designed.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record